1. Field of the Invention
The present invention relates to a laser treatment apparatus for performing photocoagulation treatment by irradiating a part to be treated, i.e., an affected part, with a laser beam for treatment.
2. Description of Related Art
As laser treatment apparatus for photocoagulation by laser irradiation, there are an apparatus of a defocusing type which performs the laser irradiation by delivering a laser beam for treatment from a laser source to a part to be treated (a treatment area) through an optical fiber without focusing an image of an exit end face of the optical fiber on the treatment area and another apparatus of a parfocal type which performs the laser irradiation while focusing the exit end face image on the treatment area. In the apparatus of the parfocal type, it an energy distribution (intensity distribution) of the laser beam is uniform at the exit end face of the optical fiber, the energy distribution on the irradiation part of the treatment area also becomes uniform. Therefore, this parfocal type apparatus is considered more preferable than the defocusing type apparatus which performs the laser irradiation with the energy distribution of the laser beam being higher on the center portion of the irradiation part than the peripheral portion.
With the use of the parfocal type apparatus, the energy distribution on the irradiation part becomes uniform, whereas the tissue of the irradiation part does not react uniformly. This may bring about a tendency to concentrate heat on the center portion, which first begins to be burned. As a result, a uniform coagulation spot could not be obtained. In particular, this remarkably appears when the spot size of the laser beam is set to be large.
The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide a laser treatment apparatus capable of producing a more uniformly coagulated state (coagulation spot) of a laser irradiation part of a treatment area.
Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the purpose of the invention, there is provided a laser treatment apparatus provided with a light delivery optical system for delivering a laser beam for treatment from a laser source to a treatment area of a patient""s eye to irradiate the treatment area, the light delivery optical system including: a homogenizer optical system which substantially uniformizes an energy distribution of the laser beam; a relay optical system having lenses for relaying an image of an exit end face of the homogenizer optical system onto the treatment area; and a distortion generating optical system which is disposed between the homogenizer optical system and the relay optical system and generates a negative distortion in the exit end face image to be formed on the treatment area.